The 280 megawatt (MW) Solana solar plant just came online in Arizona, with one unique distinction: for the first time in the U.S., the plant will use a ‘salt battery’ that will allow it to keep generating electricity even when the sun isn’t shining.

The three-square-mile commercial-scale facility near Gila Bend, Arizona will use thermal energy storage, in the form of a molten salt system, to continue producing clean energy without sunlight. “This technology enables Solana to produce electricity at full capacity for up to six hours after sunset, including the early evening hours when customer demand for power typically peaks in Arizona,” according to an Arizona Public Service (APS) press release.

This is a big step forward from the more common solar photovoltaic (PV) technology, which requires direct sunlight to create electricity.

And, as Triple Pundit notes, not only is the Solana plant a technological breakthrough in terms of thermal energy storage, it’s also the largest plant in the world to use to use parabolic trough mirrors to concentrate solar energy. This concentrated solar power (CSP) technology uses the mirrors to focus the sun’s heat on pipes, heating a synthetic oil that flows to boilers, which create the steam that drives two 140 MW turbines to produce electricity, much like a traditional power plant.

Then the thermal energy storage comes in, using molten salt to continue creating steam even when the sun goes down. “This ability to generate electricity when needed, or dispatchability, is one of the unique characteristics of concentrating solar power versus other types of renewables,” explained Abengoa Solar, the plant’s operator.

APS has already purchased all of the electricity Solana will produce, which, according to Triple Pundit, will be the equivalent of 70,000 households. And APS said that with the addition of Solana, it will increase its solar energy portfolio by nearly 50 percent and “will have 750 megawatts of solar power on its system by the end of 2013, enough to serve 185,000 Arizona customers.”

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